Conventional scanning system can be approximately divided into two segments that are handy scanning system and flat-bed scanning system. A scanning system makes use of focusing a reflecting light beam through a photodetector to generate an image signal for further image processing. A conventional scanning system apparatus includes a light source, a mirror, and a lens set, which are used to guide the reflecting light to a charge couple device (CCD). The charge couple device is utilized to generate an image signal. Typically, image capture is achieved by passing the document in front of a device known as a CCD. This consists of a large of very small, individual semiconductor receptors, disposed in a linear array. The document is passed in front of the CCD and a complete image of the document linear segments individually captured from the CCD. A pre-processing element is used to respond an image signal and adjust dc gain of the image signal. An analogue to digital converter is used to convert adjusted image signal to a digital signal and a post-processing element to generate an image code by processing said digital signal through highlight, shadow, and Gamma correction.
Conventional scanning system includes one CCD for capturing the image of a document. However, it only can be used to scan a document with small size, such as the A4 size. In order to scan a document having more larger area than A4 size, the space between the CCD and the document has to be increased. It has some drawbacks for this arrangement. For example, the size of the scanning system is increased, which can not meet the trend of scaling down the size of the scanning system. Further, the resolution and the scanning time of the scanning system are both degraded due to the space between the CCD and the document is increased.
Therefore, what is required is a scanning system having multi-CCD to scan a document with larger area, and the alignment, adjustment method of the multi-CCD for the multi-CCD scanning system.